Anterior cervical plates for spinal surgery employing anchor backout prevention devices, and related systems and methods

ABSTRACT

Anterior cervical plates for spinal surgery employing anchor backout prevention devices, and related systems and methods are disclosed. A spinal column includes vertebrae in an articulating structure. Medical intervention may involve limiting the relative motion between vertebrae by fusing at least first and second vertebrae together with osteosynthesis systems. The systems include a plate attached to anterior surfaces of the first and second vertebrae with anchors extending through passageways in the plate. By including one or more anchor backout prevention devices to the plate, movements causing the anchors to disengage from the vertebrae may be avoided. The devices may include a positioning guide, and locking magnets. The implementation of a combination of these devices into the plate may provide greater robustness against failure than any of the devices individually. In this manner, the useful life of the plate within a patient may be lengthened.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityfrom co-pending U.S. patent Ser. No. 15/205,803 filed on Jul. 8, 2016,which claims benefit of U.S. Provisional Patent Ser. No. 62/189,937filed on Jul. 8, 2015 and entitled “Cervical Plate Systems and Method ofUse,” both of which are incorporated herein by reference in theirentireties.

BACKGROUND Field of the Disclosure

The technology of the disclosure relates to osteosynthesis systems andrelated assemblies and methods for connecting bones or portions of bonesto each other in an animal, such as a human.

Technical Background

A vertebral column and a spinal cord of a patient extend from the skullto the pelvis and form a longitudinal axis of a patient. The columnincludes vertebra that are separated by fibrocartilage structures(intervertebral disks) that are interconnected with ligaments. Thevertebral column protects the spinal cord and provides structuralsupport for the patient. The spinal cord along with a bundle of nervefibers extending from the spinal cord form a central nervous systemenabling communication between the brain and other parts of the body ofthe patient. The spinal cord is protected by being disposed within avertebral canal formed by openings in each of the vertebrae. Thevertebral column typically facilitates movement of the patient byenabling relative movement between adjacent vertebrae and often servesits functions without issues, but medical intervention may involvefusing various vertebrae together in a process of stabilization toreduce pain or otherwise facilitate healing or improved quality of life.

In some interventions, anterior cervical plates may be used after ananterior arthrodesis for stabilization purposes. Bone anchors (e.g.,bone screws) may be implanted or screwed through anchor passageways inthe plates to anchor the anterior cervical plate to vertebrae toimmobilize the vertebra with respect to one another. One drawback ofconventional anterior cervical plates is that it can be difficult for anattending surgeon to accurately position the anterior cervical plateprior to affixing the anterior cervical plate with the bone anchorsand/or maintain the plate in a desired position during the implantationprocedure. Bone anchors may also have a tendency to become loose overtime, and as a result anterior cervical plates have been designed withvarious anchor backout prevention mechanisms. These backout preventionmechanisms may be cumbersome resulting in unreliable performance.Further, the mechanisms often involve a multistep engagement processthat introduces unnecessary opportunities for error and prolongs thesurgery to the detriment of the patient. Accordingly, improvements areneeded to better position cervical plates, and to more efficiently andeffectively prevent loosening of bone anchors that can uncouple theplates from vertebrae.

SUMMARY OF THE DETAILED DESCRIPTION

Embodiments disclosed herein include anterior cervical plates for spinalsurgery employing anchor backout prevention devices, and related systemsand methods. A spinal column includes vertebrae in an articulatingstructure. Medical intervention may involve limiting the relative motionbetween vertebrae by fusing at least first and second vertebrae togetherwith osteosynthesis systems. The systems include a plate attached toanterior surfaces of the first and second vertebrae with anchorsextending through passageways in the plate. By including one or moreanchor backout prevention devices to the plate, movements causing theanchors to disengage from the vertebrae may be avoided. The devices mayinclude a positioning guide, and locking magnets. The implementation ofa combination of these devices into the plate may provide greaterrobustness against failure than any of the devices individually. In thismanner, the useful life of the plate within a patient may be lengthened.

In this regard, an anterior cervical plate is disclosed having apositioning guide projecting from a rear surface of the plate. Thepositioning guide is configured such that, when positioned in the spacebetween the first and the second vertebrae and pressed against the firstvertebra, the positioning guide positively aligns the bone anchorsrelative to a corner edge (e.g., anterior corner edge) of the firstvertebra. The positive alignment provided by the positioning guidereduces the chance that the plate will slip out of position, for examplewhile the surgeon is awling holes for the bone anchors. The positioningguide facilitates optimal placement of the plate and positively alignsthe cephalad anchors (i.e. the anchors nearer the patient's head) closeto the corner edge of the first vertebra. This allows the surgeon toselect a plate with a smaller vertical extent (i.e. vertical height),maximizing the distance between the top of the plate and the next discabove it, which serves as a mechanism for reducing the chance ofadjacent level disc degeneration.

Another embodiment is disclosed that includes an anterior cervical plateincorporating a set of locking magnets providing anchor backoutprevention. The locking magnets are magnetically attracted to the headsof the bone anchors. As the bone anchors are inserted through theirrespective anchor passageways, the locking magnets or mechanismautomatically engage with the heads of the anchors to provide resistanceto the anchors backing out from the plate and the vertebrae. Theengagement of the locking magnets or mechanism with the heads of theanchors is automatic and does not require a separate additional step bythe surgeon. Moreover, the locking magnets are preferably incorporatedin the plate so as not to add bulk to the exterior profile of the plate.The provision of locking magnets in the anterior cervical plate may alsoserve to create a low magnetic field within the local bone environment,which can provide a therapeutic fusion benefit. For example, such alocal endogenous field has been found to enhance cellular bonedifferentiation. Electromagnetic fields have also been found tofacilitate bony fusion/union in high-risk patients for nonunion. Thus,incorporation of locking magnets in the locking mechanism adjacent tothe local bone environment may help expedite and/or achieve a higherrate of bony fusion development, thereby increasing the functionality ofthe plate.

In another embodiment, an anterior cervical plate is disclosed. Theanterior cervical plate includes a main body. The main body includes afront surface. The main body also includes a rear surface opposite thefront surface, wherein the rear surface is configured to face first andsecond vertebrae. The main body also includes inner surfaces connectedto the front and the rear surfaces, the inner surfaces forming first andsecond sets of anchor passageways through the main body. The anteriorcervical plate also includes a positioning guide projecting from therear surface and configured such that, when the rear surface abutsagainst an anterior surface of the first vertebra and the positioningguide abuts against an endplate of the first vertebra, the positioningguide positively aligns the first set of anchor passageways relative toan corner edge of the first vertebra. In this manner, the anteriorcervical plate may fuse the vertebrae together while avoiding backout ofthe anchors from the cervical plate.

In another embodiment, an osteosynthesis system is disclosed. Theosteosynthesis system includes an anterior cervical plate including amain body defining first and second anchor passageways and a slot, theslot partially intersecting at least one of the first and the secondanchor passageways. The osteosynthesis system further includes first andsecond anchors disposed in the first and the second anchor passageways.The osteosynthesis system further includes at least one locking magnetdisposable in the slot. The at least one locking magnet is confined tothe main body and is magnetically attracted to and engages with thefirst and second anchors so as to resist backout of the first and secondanchors from the main body when the first and second anchors areinstalled in the first and the second anchor passageways. Theosteosynthesis system can also include a coil imbedded into the slotthat intersects the anchor passageways of which can be externallystimulated to induce an electro-magnetic field for the purposes of bonehealing or fusion. In this manner, spinal surgeries can be completedwith optimal device placement while ensuring that the anterior cervicalplate is secured to the vertebrae with attachments that are strong andstable over time.

In another embodiment, a method is disclosed for installing an anteriorcervical plate of an osteosynthesis system. This method may includeabutting a rear surface of a main body of an anterior cervical plateagainst an anterior surface of a first vertebra of adjacent vertebrae,wherein the adjacent vertebrae include the first vertebra and a secondvertebra. The method may further include disposing a positioning guideof the anterior cervical plate into a voided space between the adjacentvertebrae. The method may further include pressing the positioning guideagainst an endplate of the first vertebra to position a first set ofanchor passageways of the main body relative to corner edge of the firstvertebra. The method may also include securing the main body to thefirst and the second vertebrae by implanting the first and the secondset of anchors of the osteosynthesis system into the first and thesecond vertebrae and through the first and the second set of anchorpassageways. In this manner, anterior cervical plates may be used withdimensions that are smaller than conventional plates to avoidcomplications for patients.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed description thatfollows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments, and are intendedto provide an overview or framework for understanding the nature andcharacter of the disclosure. The accompanying drawings are included toprovide a further understanding, and are incorporated into andconstitute a part of this specification. The drawings illustrate variousembodiments, and together with the description serve to explain theprinciples and operation of the concepts disclosed.

BRIEF DESCRIPTION OF THE FIGURES

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIGS. 1A through 1D are a top perspective front view, top perspectivefront exploded view, left side view, and top view of an exemplaryosteosynthesis plate system fusing first and second vertebrae together,the system including an exemplary anterior cervical plate, and boneanchors;

FIG. 1E is a left side view of the osteosynthesis plate system of FIG.1A illustrating additional vertebrae;

FIGS. 2A through 2C are front, rear and right side views, respectively,of the anterior cervical plate of FIG. 1A, including exemplarydimensions thereof;

FIGS. 3A through 3E are a front view, a rear view, a right side view, abottom sectional view, and a left sectional view, respectively, of anexemplary second anterior cervical plate which is a second embodiment ofthe anterior cervical plate of FIG. 2A, including at least one exemplarylocking magnet fixed to the main body of the second anterior cervicalplate;

FIGS. 4A through 4C are a top view, a front view, and a left side viewof the at least one locking magnet of FIG. 3A;

FIGS. 5A and 5B are bottom sectional views of exemplary bone anchorscoupled to the second anterior cervical plate of FIG. 3A, wherein outersurfaces of heads of the bone anchors includes linear and curvedprofiles, respectively;

FIG. 5C is a right side view of the anterior cervical plate of FIG. 3Afusing the first and second vertebrae together, wherein the at least onelocking magnet creates a magnetic field;

FIG. 5D is a right side view of the anterior cervical plate system ofFIG. 3A fusing the first and second vertebrae together, wherein the atleast one locking magnet creates a magnetic field under the influence ofa stimulator and the at least one locking magnet includes anelectromagnet;

FIG. 5E is a schematic view of the stimulator of FIG. 5D inducing theelectromagnet of FIG. 5D to produce the magnetic field;

FIGS. 6A-1 and 6A-2 are a front view and a bottom sectional view,respectively, of an exemplary third anterior cervical plate which is athird embodiment of the anterior cervical plate of FIG. 2A, including atleast one exemplary locking magnet movable relative to a main body ofthe third anterior cervical plate, wherein the locking magnets areillustrated in open positions;

FIGS. 6B-1 and 6B-2 are a front view and a bottom sectional view,respectively, of the third anterior cervical plate of FIG. 6A-1, whereinthe locking magnets are illustrated in closed positions;

FIGS. 7A through 7C are a front view, a bottom view, and a left sideview, respectively, of one of the locking magnets of FIG. 6A-1;

FIGS. 8A and 8B are a front view and a bottom sectional view,respectively, of an exemplary fourth anterior cervical plate which is afourth embodiment of the anterior cervical plate of FIG. 2A, includingat least one exemplary locking magnet movable relative to the main bodyof the fourth anterior cervical plate and at least one secondary magnet,wherein the locking magnets are illustrated in open positions;

FIG. 8C is a bottom sectional view of the fourth anterior cervical plateof FIG. 8B engaged with a bone anchor, wherein the locking magnet isshown in a closed position coupled to a head of the bone anchor;

FIGS. 9A through 9D are a front view, a rear view, a right side view,and a sectional view, respectively, of an exemplary fifth anteriorcervical plate which is a fifth embodiment of the anterior cervicalplate of FIG. 2A;

FIG. 9E is a right side view of the anterior cervical plate of FIG. 9Afusing adjacent vertebrae together, wherein the stimulator of FIG. 5Dinduces an electromagnet to produce the magnetic field;

FIG. 10 is a flowchart of an exemplary method of fusing adjacentvertebrae with a osteosynthesis plate system consistent with thisdisclosure; and

FIGS. 11A and 11B are an anterior view and a right side view,respectively, of an exemplary sixth osteosynthesis plate systemincluding a sixth anterior cervical plate that is a sixth embodiment ofthe anterior cervical plate of FIG. 2A and may fuse more than twovertebrae together.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples ofwhich are illustrated in the accompanying drawings, in which some, butnot all embodiments are shown. Indeed, the concepts may be embodied inmany different forms and should not be construed as limiting herein;rather, these embodiments are provided so that this disclosure willsatisfy applicable legal requirements. Whenever possible, like referencenumbers will be used to refer to like components or parts.

Embodiments disclosed herein include anterior cervical plates for spinalsurgery employing anchor backout prevention devices and integratedosteosynthesis capacity through electro-magnetic stimulation, andrelated systems and methods. A spinal column includes vertebrae in anarticulating structure. Medical intervention may involve limiting therelative motion between vertebrae by fusing at least first and secondvertebrae together with osteosynthesis systems. The systems include aplate attached to anterior surfaces of the first and second vertebraewith anchors extending through passageways in the plate. By includingone or more anchor backout prevention devices to the plate, movementscausing the anchors to disengage from the vertebrae may be avoided. Thedevices may include a positioning guide, and locking magnets. Theimplementation of a combination of these devices into the plate mayprovide greater robustness against failure than any of the devicesindividually. In this manner, the useful life of the plate within apatient may be lengthened.

In this regard, FIGS. 1A through 1D are a top perspective front view,top perspective front exploded view, left side view, and top view of anexemplary osteosynthesis plate system 10 fusing first and secondvertebrae 12X, 12Y together. Also, FIG. 1E is a left side view of theosteosynthesis plate system 10 of FIG. 1A illustrating additionalvertebrae 12W, 12Z. The fusing of the vertebrae 12X, 12Y may occur, forexample, for stabilization purposes after an anterior arthrodesis tobridge a discectomy voided space 13 between the first and the secondvertebrae 12X, 12Y. The osteosynthesis plate 10 may have severalcomponents.

The osteosynthesis plate system 10 may include an anterior cervicalplate 14, a first set of bone anchors 16A, 16B, and a second set of boneanchors 16C, 16D. The anterior cervical plate 14 includes a main body 18with a front surface 20A and a rear surface 20B opposite the frontsurface 20A. The main body 18 also includes inner surfaces 22A-22Drespectively forming anchor passageways 24A-24D extending from the frontsurface 20A to the rear surface 20B. The bone anchors 16A-16D includeheads 26 and distal ends 28 coupled to the heads 26. The heads 26 areconfigured to interface with an anchor installation tool (e.g., torquedriver) and to interface with the main body 18 of the anterior cervicalplate 14 while the distal ends 28 are configured to form attachments 25with the vertebrae 12X, 12Y.

In one embodiment, the bone anchors 16A-16D may respectively includebone screws 30A-30D. The distal ends 28 may include, for examplethreaded distal ends 32, which are disposed through the anchorpassageways 24A-24D (along the center axes AO of the anchor passageways24A-24D) and into the first and the second vertebrae 12X, 12Y where theyform the attachments 25 with the first and the second vertebrae 12X,12Y. These attachments 25 are based on at least one of: friction,mechanical interference, cohesive bonds, and adhesive bonds. Also, theseattachments 25 resist the withdrawal of the distal ends 28 from thefirst and the second vertebrae 12X, 12Y and hold or secure the boneanchors 16A-16D in positions stationary relative to the vertebrae 12X,12Y.

Moreover, a width W1 of the heads 26 is greater than a minimum width W2of the anchor passageways 24A-24D to enable the heads 26 to formmechanical interferences 29 (FIGS. 1C and 1D) with the main body 18 andthereby prevent the main body 18 from disengaging and backing out fromthe bone anchors 16A-16D and the first and the second vertebrae 12X,12Y. After the attachments 25 are formed, the bone anchors 16A-16D maybe implanted within the vertebrae 12X, 12Y such that the distal ends 28are in tension to pull the heads 26 of the bone anchors 16A-16D towardsthe vertebrae 12X, 12Y and against the anterior cervical plate 14. Thispulling of the heads 26 against the anterior cervical plate 14 towardsthe vertebrae 12X, 12Y holds the anterior cervical plate 14 staticagainst respective anterior surfaces 27X, 27Y of the first and thesecond vertebrae 12X, 12Y with a force Fc (FIG. 1A).

Other details of the anterior cervical plate 14 of FIG. 1A are nowprovided. FIGS. 2A through 2C are front, rear and right side views,respectively, of the anterior cervical plate 14 of the osteosynthesisplate system 10 according to an embodiment, including exemplarydimensions thereof. The anterior cervical plate 14 also includes apositioning guide 36, and bone anchors 16A-16D. The positioning guide 36projects from the rear surface 20B of the main body 18. The rear surface20B may include a plurality of slots 46A, 46B for receiving lockingmagnets 42A, 42B. The operation of the locking magnets 42A, 42B will bedescribed later relative to FIG. 3A.

The positioning guide 36 may be formed independently and attached to themain body 18 or formed integrally therewith. The positioning guide 36 issized to fit between adjacent vertebrae 12X, 12Y being fused by theanterior cervical plate 14 (FIG. 1C). The first and the second vertebrae12X, 12Y may be the C5 and C6 vertebrae. In use, the positioning guide36 is inserted into a discectomy voided space 13 between the adjacentvertebrae 12X, 12Y and then pressed against the first vertebra 12X(illustrated as C5), so that a first abutment surface 38A of thepositioning guide 36 rests or abuts against an endface 37X (e.g.,underside) of the first vertebra 12X and the rear surface 20B of themain body 18 rests or abuts against an anterior surface 27X of the firstvertebra 12X, as is illustrated in FIG. 1C. In this orientation, theanchor passageways 24A, 24B are aligned so that the bone anchors 16A,16B passing through the anchor passageways 24A, 24B enter the firstvertebra 12X (e.g., C5) a distance X4 (FIG. 2C) from a corner edge 39X(FIG. 1C), for example, an inferior corner edge of the first vertebra12X. The corner edge 39X is formed by the anterior surface 27X of thefirst vertebra 12X and the endface 37X of the first vertebra 12X. Thus,the positioning guide 36 may provide a positive stop that positions theanchor passageways 24A, 24B in an ideal location for subsequentinsertion or implantation of the bone anchors 16A, 16B into the firstvertebra 12X.

Prior to anchor implantation (or insertion), and while the anteriorcervical plate 14 is held in the ideal position relative to the firstvertebra 12X, the attending surgeon may form pilot holes (not shown) inthe first vertebra 12X for the bone anchors 16A, 16B to be implanted byinserting a suitable hole forming instrument, for example, an awl (notshown) or a screw tap (not shown) through the upper anchor passageways24A, 24B in the main body 18 and into the first vertebra 12X. Thepositive positioning provided by the positioning guide helps to maintainthe anterior cervical plate 14 in position through this process andthereby reduces the chances that the attending surgeon will form thepilot holes in the wrong locations.

It is also noted that the positioning guide 36 may also serve as abackout prevention device for the bone anchors 16A, 16B by helping holdthe anterior cervical plate 14 fixed relative to the first vertebra 12Xin the case that one of the attachments 25 of the bone anchors 16A, 16Bfails. Movement of the anterior cervical plate 14 relative to the firstvertebra 12X may cause the remaining attachment 25 of the bone anchors16A, 16B that has not yet failed to weaken prematurely and theassociated bone anchor to backout of the anterior cervical plate 14. Inthis manner, the positioning guide 36 may prevent backout of the boneanchors.

Moreover, because the anchor passageways 24A, 24B are positivelypositioned relative to the corner edge 39X of the first vertebra 12X,the attending surgeon does not need to select a size of the anteriorcervical plate 14 that mounts the bone anchors 16A, 16B further awayfrom the corner edge 39X of the first vertebra 12X due to theuncertainties of being able to accurately position the bone anchors 16A,16B any closer to the corner edge 39X. Accordingly, the ability to moreprecisely position the bone anchors 16A, 16B relative to the firstvertebra 12X allows the attending surgeon to select an anterior cervicalplate 14 with a smaller vertical extent Dz, and thereby maximize adistance X6 (FIG. 1E) between the anterior cervical plate 14 and aneighboring vertebra 12W (i.e., C4) disposed superior to the adjacentvertebrae 12X, 12Y. Maximizing the distance X6 is advantageous, assmaller values of the distance X6 have been found to be associated withincreased chances of adjacent level disc degeneration, or in other wordsdegeneration of the vertebra 12W. Thus, maximizing the distance X6 mayreduce the chances of adjacent level disc degeneration or othercomplications.

With reference back to FIGS. 1C and 1D, the bone anchors 16A, 16B andthe bone anchors 16C, 16D may have fixed insertion angle trajectoriesor, as illustrated, the bone anchors 16A, 16B and the bone anchors 16C,16D may be variable angle trajectories. Preferably, the bone anchors16A, 16B and upper anchor passageways 24A, 24B may be designed toaccommodate a first insertion angle θ₁ (theta_1) measured as an angulardifference within a sagittal plane P2 of the center axis AO with respectto a vector n1 orthogonal to the main body 18. The first insertion angleθ₁ (theta_1) may be within a range from minus twenty-five (−25) degreesto plus twenty-five (+25) degrees. Further, the bone anchors 16A, 16Band the bone anchors 16C, 16D may also be inserted at second insertionangles θ₂ (theta_2) measured as an angular difference within atransverse plane P2 of the center axis AO with respect to a vector n1orthogonal to the main body 18. The second insertion angle θ₂ (theta_2)may be within a range from minus twenty-five (−25) degrees to plustwenty-five (+25) degrees. In this manner, the attending surgeon mayselect the first and second insertion angles θ₁, θ₂ of the bone anchors16A, 16B and the bone anchors 16C, 16D to most securely attach theanterior cervical plate 14 to the adjacent vertebrae 12X, 12Y.

The osteosynthesis plate system 10 may also include at least one otherbackout prevention device for the bone anchors 16A, 16B and the boneanchors 16C, 16D. In this regard, FIGS. 3A through 3E are a front view,a rear view, a right side view, a bottom sectional view, and a leftsectional view, respectively, of an exemplary second anterior cervicalplate 14P that is a second embodiment of the anterior cervical plate 14of FIG. 2A, including the backout prevention device. This deviceincludes at least one exemplary locking magnet 42A, 42B fixed to themain body 18 of the second anterior cervical plate 14P. In this regard,the anterior cervical plate 14 may include slot surfaces 44A, 44Bforming slots 46A, 46B. The locking magnets 42A, 42B are preferablymounted in the slots 46A, 46B in the anterior cervical plate 14 so as toavoid or minimize additional bulk to be added to a side view profile(FIG. 3C) of the anterior cervical plate 14P in comparison to the sideview (FIG. 2C) of the anterior cervical plate 14. The slots 46A, 46B andthe slot surfaces 44A, 44B may be disposed in the rear surface 20B ofthe anterior cervical plate 14 (not shown), or in the front surface 20Aof the anterior cervical plate 14, as shown in FIG. 3A. The slot 46Aintersects with the anchor passageways 24A, 24B and allows magnet ends48A, 48B of the locking magnet 42A to come in contact with or in closeproximity with heads 26 of the bone anchors 16A, 16B. Further, the slot46B intersects with the anchor passageways 24C, 24D and allows magnetends 48A, 48B of the locking magnet 42B to come in contact with or inclose proximity with heads 26 of the bone anchors 16C, 16D. FIGS. 4Athrough 4C are a top view, a front view, and a left side view of anon-limiting embodiment of the at least one locking magnet of FIG. 3A.

With continued reference to the embodiment shown in FIGS. 3A through 3E,the locking magnet 42A may fixed in the slot 46A extending between theupper anchor passageways 24A, 24B and the locking magnet 42B is fixed inthe slot 46B extending between the lower anchor passageways 24C, 24D.The locking magnets 42A, 42B may be fixed in the slots 46A, 46B in anyfashion, for example, such as via a press fit, glue (adhesive orcohesive), soldering, and/or welding. Alternatively the anteriorcervical plate 14P may include at least one cover plate (not shown inFIGS. 3A through 3E) attached to the front surface 20A or rear surface20B of the main body 18 to contain the locking magnets/mechanism 42A,42B within the slots 43A, 43B without escaping. In these exemplaryapproaches, the locking magnets 42A, 42B may be attached to the anteriorcervical plate 14P.

The backout prevention device may be further configured to increasebackout protection between the locking magnet 42A and the bone anchors16A, 16B and between the locking magnet 42B and the bone anchors 16C,16D. In this regard, FIGS. 5A and 5B are bottom sectional views ofexemplary bone anchors coupled to the second anterior cervical plate ofFIG. 3A as part of a osteosynthesis plate system 10P, wherein outersurfaces of heads of the bone anchors include linear and curvedprofiles, respectively. Accordingly, the magnet ends 48A, 48B of thelocking magnet 42A may be curved or shaped to match shapes or curvatures49 of outer surfaces 50A, 50A′ of the heads 26 of the bone anchors 16A,16B, and the heads 26 are magnetized such that the magnet ends 48A, 48Bof the locking magnet 42B and the heads 26 are magnetically attracted toeach other to prevent backout of the bone anchors 42A-42D from theanterior cervical plate 14P. In operation, as each of the bone anchors16A, 16B are inserted in the anchor passageways 24A, 24B, the respectiveone of the heads 26 advances into the anterior cervical plate 14P untilmeeting one of the magnet ends 48A, 48B of the locking magnet 42Aincorporated in the slot 46A in the anterior cervical plate 14P.Similarly, as each of the bone anchors 16C, 16D are inserted in theanchor passageways 24C, 24D, the respective one of the heads 26 advancesinto the anterior cervical plate 14P until meeting one of the magnetends 48A, 48B of the locking magnet 42B incorporated in the slot 46B ofthe anterior cervical plate 14P. Because the locking magnets 42A, 42Bare confined or coupled to the slots 46A, 46B of the anterior cervicalplate 14P, the magnetic attraction (or magnetic force) between the heads26 of the bone anchors 16A-16D and at least one of the locking magnets42A, 42B serves to resist the bone anchors 16A-16D backing out of theanterior cervical plate 14P. In this manner, complications related tothe bone anchors 16A-16D desirably uncoupling from the anterior cervicalplate 14P may be avoided.

FIG. 5C is a right side view of the anterior cervical plate of FIG. 3Afusing the first vertebra 12X and the second vertebra 12Y together,wherein the locking magnets 42A, 42B creates a magnetic field 72. Themagnetic field 72 may be disposed in the attachments 25 of the firstvertebra 12X and the second vertebra 12Y to facilitate an accelerationof the healing of the bone tissues to improve the strength of theattachments 25. The magnetic field 72 may also be created to penetratebone graft material 70 located in the discectomy voided space 13. Themagnetic flux 72 created by the locking magnets 42A, 42B may through aprocess of osteogenesis facilitate an accelerated integration of thebone graft material 70 by the first vertebra 12X and the second vertebra12Y. In this manner, the first vertebra 12X and the second vertebra 12Ymay fuse together quicker and reduce stress on the anterior cervicalplate 14.

The magnetic field 72 may be created differently based on the type oflocking magnet used (i.e., permanent magnet and/or electromagnet). FIG.5D is a right side view of the anterior cervical plate of FIG. 3A fusingthe first vertebra 12X and the second vertebrae 12Y together, whereinthe locking magnets 42A, 42B create the magnetic field 72 under theinfluence of a stimulator 74 and the locking magnets 42A, 42B includesat least one electromagnet 73A, 73B. The stimulator 74 may be moved bymedical personnel outside the patient and proximate to the lockingmagnets 42A, 42B including the electromagnets 73A, 73B. The stimulator74 may create magnetic field 76 that induces the electromagnets 73A tocreate the magnetic field 72 that may be more precisely located relativeto the attachments 25 and the bone graft material 70 than may beconveniently possible with the magnetic field 76 of the stimulator 74.In this manner, the magnetic field 72 may be better directed tofacilitate healthy bone formation and development at the attachments 25and the bone graft material 70.

Details of the stimulator 74 and the electromagnets 73A are nowdescribed. FIG. 5E is a schematic view of the stimulator 74 of FIG. 5Dinducing in a non-limiting embodiment the electromagnet 73C to producethe magnetic field 76. The stimulator 74 may include components tocreate static or dynamic magnetic field 76 to induce the electromagnets73A, 73B fixed to the anterior cervical plate 14P to produce themagnetic field 72. In one embodiment, the stimulator 74 may include theelectromagnet 73C powered by a power source 78 (i.e., alternativecurrent power supply). The electromagnet 73C may include a conductivewire 80 wrapped around a metal bar 82. The conductive wire 80 may becoupled to the power source 78 configured to produce an electricalcurrent in the conductive wire 80. Accordingly, a magnetic field 76 iscreated as the electrical current travels along the conductive wire 80formed with turns about the metal bar 82. As the stimulator 74 may beplaced in proximity to the electromagnets 73A, 73B fixed to the anteriorcervical plate 14P, the electromagnets 73A, 73B may produce the magneticfield 72. Each of the electromagnets 73A, 73B may include a conductivewire 84 wrapped around a metal bar 86. Ends of the conductive wire 84may also in some non-limiting embodiments be coupled to a resistiveelement (not shown) to form a closed circuit. The electromagnets 73A,73B may be fixed within the slots 46A, 46B as similarly discussed abovewith the locking magnets 42A, 42B. Upon receiving the magnetic field 76from the stimulator 74, a static or dynamic electrical current may begenerated in the conductive wire 84 through induction. This electricalcurrent induced in the conductive wires 84 may cause the magnetic field72 to be created. In this manner, the magnetic field 72 may be createdto facilitate osteogenesis of the attachments 25 and the bone graftmaterial 70.

Other embodiments are possible to avoid desirable uncoupling of the boneanchors 16A-16D. FIGS. 6A-1 and 6A-2 are a front view and a bottomsectional view, respectively, of an exemplary third anterior cervicalplate 14PP which is a third embodiment of the anterior cervical plate 14of FIG. 2A. The plate 14PP includes at least one exemplary lockingmagnet 42A(1), 42A(2), 42B(1), 42B(2) movable relative to the main body18 of the third anterior cervical plate 14PP, wherein these lockingmagnets are illustrated in open positions 57A. These locking magnets aretranslatable (or otherwise movable) within the slots 46A(1), 46A(2),46B(2), 46B(2) of the anterior cervical plate 14PP, providing a dynamiclocking mechanism. Each of the bone anchors 16A-16D includes the head 26that accommodates a conventional insertion tool (not shown) and a distalend 28 coupled to the head 26. Between the head 26 and the distal end28, each of the bone anchors 16A-16D defines a circumferential lip 53coupling the head 26 to the distal end 26. The circumferential lip 53may be used as one of many interfaces to prevent the desired uncouplingof the bone anchor from the anterior cervical plate 14PP.

The locking magnets 42A(1), 42A(2), 42B(1), 42B(2) may be used tointerface with the circumferential lips 53 of the bone anchors. Thelocking magnets 42A(1), 42A(2), 42B(1), 42B(2) are confined to the slots46A(1), 46A(2), 46B(1), 46B(2) by at least one cover plate 54A, 54B (orretention plate), so that these locking magnets can each translate (ormove) back and forth within the slots, respectively, as illustrated inFIG. 6A-1. In this regard, the locking magnets 42A(1), 42A(2), 42B(1),42B(2) translate between an open position 57A that accommodates passageof the circumferential lip 53 away from the anterior cervical plate 14and a closed position 57B that does not accommodate passage of thecircumferential lip 53 from the anterior cervical plate 14. FIGS. 7Athrough 7C are a front view, a bottom view, and a left side view,respectively, of the locking magnet 42A(1) of FIG. 6A-1. FIGS. 6B-1 and6B-2 are a front view and a bottom sectional view, respectively, of thethird anterior cervical plate of FIG. 6A-1, wherein the locking magnetsare illustrated in closed positions 57B. For each of the bone anchors16A-16D inserted in respective ones of the anchor passageways 24A-24Dwhere the circumferential lips 53 advance past the locking magnets42A(1), 42A(2), 42B(1), 42B(2), the locking magnets 42A(1), 42A(2),42B(1), 42B(2) are magnetically attracted to the head 26 or anchorposition and at least one of the locking magnets 42A(1), 42A(2), 42B(1),42B(2) are drawn into contact with each of the heads 26 by virtue of themagnet attraction (magnetic force FM1), bringing the at least onelocking magnet 42A(1), 42A(2), 42B(1), 42B(2) into the closed position57B. With the locking magnets 42A(1), 42A(2), 42B(1), 42B(2) in contactwith the heads 26 of the bone anchors 16A-16D, the locking magnets42A(1), 42A(2), 42B(1), 42B(2) block passages of the circumferentiallips 53 (by forming mechanical interferences) and thereby prevent thebone anchors 16A-16D from backing out of the anterior cervical plate 14.If the attending surgeon wishes to allow the bone anchors 16A-16D toback out, the attending surgeon can manually push the locking magnets42A(1), 42A(2), 42B(1), 42B(2) out of the way of the circumferentiallips 53 to allow the bone anchors 16A-16D to be removed (not shown).

In another embodiment, the locking magnets 42A(1), 42A(2), 42B(1),42B(2) may be biased to remain in the open position 57A. In this regard,FIGS. 8A and 8B are a front view and a bottom sectional view,respectively, of an exemplary fourth anterior cervical plate 14PPP whichis a fourth embodiment of the anterior cervical plate 14 of FIG. 2A. Thefourth anterior cervical plate 14PPP includes the locking magnets42A(1), 42A(2), 42B(1), 42B(2) movable relative to the main body 18 ofthe fourth anterior cervical plate 14PPP and at least one secondarymagnet 58A-58D, wherein the locking magnets are illustrated in openpositions 57A. Accordingly, this biasing may be accomplished byproviding the secondary magnets 62A, 62B at opposite ends of the slots46A, 46B from the anchor passageways 24A-24D. The locking magnets42A(1), 42A(2), 42B(1), 42B(2) may be weakly attracted to the secondarymagnets 58A-58D with a secondary magnetic force FM2. The magnetic forceFM1 between an operative end 48A of the each of the locking magnet 42A,42B and the heads 26 of the bone anchors 16A-16D may be greater than themagnetic force FM2. Thus, the magnetic force FM2 is then strong enoughto draw the locking magnets 42A(1), 42A(2), 42B(1), 42B(2) into theclosed positions 57B only when the heads 26 of the of the bone anchors16A-16D has been inserted into the anchor passageways 24A-24D of theanterior cervical plate 14PPP. For example, FIG. 8C is a bottomsectional view of the fourth anterior cervical plate 14PPP of FIG. 8Bengaged with the bone anchor 16A, wherein the locking magnet 42A(1) isshown in a closed position 57B and coupled to the head 26′ of the boneanchor 16A.

It is to be appreciated in this disclosure that the anterior cervicalplate 14 and the locking magnets 42A(1), 42A(2), 42B(1), 42B(2) and thesecondary magnets 58A-58D, may include materials appropriate forlong-term implantation in a patient 66. For example, the non-magneticcomponents, such as the anterior cervical plate 14PPP, the distal ends28 of the bone anchors 16A-16D, and the cover plates 54A, 54B mayinclude titanium. The magnets 42A, 42B and the secondary magnets 58A-58Dmay include permanent magnets constructed of biocompatible, autoclavableand oxidative resistive alloys. Also, while it is preferred that theanterior cervical plates 14 may incorporate both the positioning guide36 and the locking magnets 42A(1), 42A(2), 42B(1), 42B(2) describedherein, anterior cervical plates 14 are also envisioned that incorporateone or the other. For example, anterior cervical plates 14 using thepositioning guide 36 may alternatively utilize any known anchor backoutprevention devices, and anterior cervical plates using the lockingmagnets 42A(1), 42A(2), 42B(1), 42B(2) may be provided with or withoutthe positioning guide 36.

Other embodiments are possible of the anterior cervical plate 14. FIGS.9A through 9D are a front view, a rear view, a right side view, and asectional view, respectively, of an exemplary fifth anterior cervicalplate 14PPPP which is a fifth embodiment of the anterior cervical plateof FIG. 2A. The anterior cervical plate 14PPPP is similar to theanterior cervical plate 14 of FIG. 2A and so mainly differences will bediscussed in the interests of clarity and conciseness. The anteriorcervical plate 14PPPP may include the locking magnet 42A embedded withinor fixed to the positioning guide 36 to form a positioning guide 36P.The locking magnet 42A may include at least one of a permanent magnet oran electromagnet. In the embodiment illustrated in FIG. 9E, the lockingmagnet 42A may include the electromagnet 73A including the conductivewire 84 wrapped around the metal bar 86. In this manner, when theelectromagnet 73A is placed in the magnetic field 76 of the stimulator74, then the electromagnet 73A may create a magnetic field 72 proximateto the bone graft material 70, so that formation and generation oftissue in combination with the bone graft material 70 may facilitate thefusing together of the first vertebra 12X and the second vertebra 12Y.

Thus, aside from using locking magnets to prevent bone anchors frombacking out of the main body 18 of the anterior cervical plate 14, thelocking magnets may also have the ability to generate anelectro-magnetic field due to intrinsic properties—ie. functioning as atransducer or through a plate imbedded coil stimulated via an externalsignal generator (i.e., stimulator 74). Moreover, such an inherentproperty of such a device/plate or other orthopaedic and or spineimplant, rod system, may thus generate an electro-magnetic field toenhance osteogenesis. This may be through an outside or implantablesignal generator and be applicable to cervical, anterior lumbar orthoraco-lumbar or other orthopaedic anatomically instrumentedapplications.

FIG. 10 is a flowchart of an exemplary method 900 for fusing theadjacent vertebrae 12X, 12Y during spinal surgery consistent with theosteosynthesis plate systems of disclosed herein. The method 900 is nowdiscussed using the terminology discussed above and below in relation tothe operations 902A through 902H as depicted in FIG. 10. In this regard,the method 900 may include abutting a rear surface of a main body of ananterior cervical plate against an anterior surface of a first vertebraof adjacent vertebrae, wherein the adjacent vertebrae include the firstvertebra and a second vertebra (operation 902A of FIG. 10). The methodmay also include disposing a positioning guide of the anterior cervicalplate projecting from the rear surface within a voided space between theadjacent vertebrae (operation 902B of FIG. 10). The method may alsoinclude pressing the positioning guide against an endplate of the firstvertebra so as to position a first set of anchor passageways of the mainbody relative to an anterior inferior corner edge of the first vertebra(operation 902C of FIG. 10). The method may also include while theposition guide is placed against the first vertebra, using the first setof anchor passageways as guides to form holes, such as with an awl, inthe upper vertebra for receiving the first set of anchors (operation902D of FIG. 10). The method may also include securing the main body tothe first and the second vertebrae by implanting first and second boneanchors of the osteosynthesis system into the first and the secondvertebrae and respectively through the first and the second set ofanchor passageways (operation 902E of FIG. 10). The method may alsoinclude upon the implanting the first and second set of anchors,applying a magnetic force to the first and second set of bone anchorswith locking magnets coupled to the anterior cervical plate. (operation902F of FIG. 10). The method may also include moving the locking magnetstowards the first and second none anchors with the magnetic force.(operation 902G of FIG. 10). The method may also include forming, withgrooves in the locking magnets, mechanical interferences with the firstand second none anchors. (operation 902H of FIG. 10). In this manner,the vertebrae may be fused while avoiding unwanted decoupling of theplate from the vertebrae.

While described in connection with fusion of vertebra, it is to beunderstood that an anchor (or screw) backout prevention device usingmagnets as described herein can be used in other applications. Forexample, any long bone or high risk for nonunion orthopedic fracturerequiring internal fixation with an implant that is secured with boneanchors could benefit from incorporating a magnet lock backoutprevention mechanism.

Also, while described in the context of an anterior cervical platedesigned for use in securing two vertebras, it is to be understood thatthe embodiments of this disclosure can be applied to plates used inmulti-level fusions, for example securing 3 or 4 vertebrae. FIGS. 11Aand 11B are an anterior view and a right side view, respectively, of anexemplary sixth osteosynthesis plate system 10′ including a sixthanterior cervical plate 14′ that is a sixth embodiment of the anteriorcervical plate 14 of FIG. 2A and may fuse more than two vertebraetogether. In multilevel degenerative disc disease, multilevelreconstruction, decompression can be performed with instrumentation.With multilevel fusion, inherent nonunion rates have also been describedas higher, thus adding magnetic field plate capability may enhance unionsuccess. This multi-level version of the plate 14′ may be used in thefusion of vertebrae 12X, 12E, 12G, 12Y (for example multiple discsC4-C7). The anterior cervical plate 14′ includes the positioning guide36 projecting from the rear surface 20B that is placed against theanterior inferior corner 39X of the upper most disc being fused, whichin this case may be C4. The anterior cervical plate 14′ is configuredwith a vertical extant DZ to span the multiple discs. The anteriorcervical plate 14′ may include at least one viewing window 99(1)-99(N1).The viewing windows 99(1)-99(N1) include transparent material to enablethe attending surgeon to see therethrough for viewing bone grafts70(1)-70(3) that may be placed or installed between the vertebrae 12X,12E, 12G, 12Y to be fused in the conventional fashion. Bone anchors16A-16H (e.g., bone screws) secure the anterior cervical plate 14′ toeach level, and disposed between each set of the bone anchors 16A-16H ofa level, one or more locking magnets 42 and perhaps also secondarymagnets (not shown) are provided in one or more slots 46 (or channels)in the main body 18′ of the anterior cervical plate 14′ to lock the boneanchors 16A-16H in position, as described similarly above to preventbackout of the bone anchors 16A-16H from the main body 18′.

Many modifications and other embodiments not set forth herein will cometo mind to one skilled in the art to which the embodiments pertainhaving the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. Therefore, it is to beunderstood that the description and claims are not to be limited to thespecific embodiments disclosed and that modifications and otherembodiments are intended to be included within the scope of the appendedclaims. It is intended that the embodiments cover the modifications andvariations of the embodiments provided they come within the scope of theappended claims and their equivalents. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

What is claimed is:
 1. An anterior cervical plate, comprising: a mainbody including a front surface and a rear surface opposite the frontsurface, wherein the rear surface is configured to face first and secondvertebrae; and a positioning guide projecting from the rear surface,wherein the positioning guide is configured such that, when the rearsurface abuts against anterior surfaces of the first and the secondvertebrae and the positioning guide abuts against an endplate of thefirst vertebra, the positioning guide is configured to be free fromabutment against the second vertebra.
 2. The anterior cervical plate ofclaim 1, wherein the first vertebra is disposed superior to the secondvertebra.
 3. The anterior cervical plate of claim 1, wherein thepositioning guide projects from the rear surface a distance in a rangefrom one (1) millimeter to four (4) millimeters.
 4. The anteriorcervical plate of claim 1, further comprising inner surfaces connectedto the front and the rear surfaces, wherein the inner surfaces formingform a first anchor passageway and a second anchor passageway throughthe main body, wherein the first and the second anchor passageways areconfigured to respectively receive first and second anchors.
 5. Theanterior cervical plate of claim 4, wherein the positioning guide isdisposed between center axes of the first and the second anchorpassageways.
 6. The anterior cervical plate of claim 1, wherein thepositioning guide includes an abutment surface configured to abutagainst the first vertebra, and the abutment surface includes a width ina range from five (5) millimeters to fifteen (15) millimeters.
 7. Theanterior cervical plate of claim 1, wherein the positioning guide isintegral with the main body.
 8. The anterior cervical plate of claim 1,wherein the rear surface is substantially disposed in a geometric plane.9. A method, comprising: abutting a rear surface of a main body of ananterior cervical plate against anterior surfaces of first and secondvertebrae; and abutting a positioning guide against an endplate of thefirst vertebra while the positioning guide is free from abutment withthe second vertebra, wherein the positioning guide projects from therear surface.
 10. The method of claim 9, further comprising receiving afirst anchor in a first anchor passageway and forming a first attachmentwith the first vertebra while the positioning guide abuts against theendplate of the first vertebra, wherein an inner surface of the mainbody forms the first anchor passageway and the inner surface isconnected to the rear surface and a front surface of the main bodyopposite the rear surface.
 11. The method of claim 10, furthercomprising receiving a second anchor in a second anchor passageway andforming a second attachment with the second vertebra while thepositioning guide abuts against the endplate of the first vertebra,wherein a second inner surface of the main body forms the second anchorpassageway and the second inner surface connects the rear surface andthe front surface.
 12. The method of claim 11, wherein the positioningguide is disposed between center axes of the first and the second anchorpassageways.
 13. The method of claim 9, wherein the first vertebra isdisposed superior to the second vertebra.
 14. The method of claim 9,wherein the positioning guide is integral with the main body.
 15. Themethod of claim 9, wherein the positioning guide projects from the rearsurface a distance in a range from one (1) millimeter to four (4)millimeters.
 16. The method of claim 9, wherein the positioning guide isintegral with the main body.
 17. The method of claim 9, wherein the rearsurface is substantially disposed in a geometric plane.